package com.xuwei.ext.proxy;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Arrays;

/**
 * 计算器日志打印动态代理类
 * @author xu
 *
 */
public class ArithmeticCalculatorLoggingProxy {
	//要代理的对象
	private ArithmeticCalculator target;
	public ArithmeticCalculatorLoggingProxy(ArithmeticCalculator target){
		super();
		this.target = target;
	}
	
	//返回代理对象
	@SuppressWarnings("rawtypes")
	public ArithmeticCalculator getLoggingProxy(){
		ArithmeticCalculator proxy = null;
		ClassLoader loader = target.getClass().getClassLoader();
		Class[] interfaces = new Class[]{ArithmeticCalculator.class};
		InvocationHandler h = new InvocationHandler() {
			
			@Override
			public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
				String methodName = method.getName();
				//打印日志方法
				System.out.println("[before] The method "+methodName+" begins with "+Arrays.asList(args));
				//调用目标方法
				Object result = null;
				try {
					//前置通知
					
					result = method.invoke(target, args);
					//返回通知，可以访问方法的返回值 
					
				} catch (Exception e) {
					e.printStackTrace();
					//异常通知，可以访问到方法出现的异常
					
				}
				//后置通知，因为方法可能会出现异常，所以访问不到方法的返回值
				//打印日志
				System.out.println("[after] The method ends with "+result);
				return result;
			}
		};
		
		/**
		 * loader:代理对象使用的类加载器
		 * interfaces: 指定代理对象的类型，即代理对象中可以有哪些方法
		 * h：当具体调用代理对象的方法时，应该如何进行响应，实际上就是调用InvocationHandler的invoke的方法
		 */
		proxy = (ArithmeticCalculator)Proxy.newProxyInstance(loader, interfaces, h);
		return proxy;
	}
	
	public static void main(String[] args) {
		ArithmeticCalculator arithmeticCalculator = new ArithmeticCalculatorLoggingProxy(
				new ArithmeticCalculatorImpl()).getLoggingProxy();
		int result =	arithmeticCalculator.add(5, 8);
		System.out.println(result);
		result = arithmeticCalculator.mult(9, 14);
		System.out.println(result);
		
		
		
		
	}
	
}
